Google Chrome is sponsoring the free service.

Orlando-based AirTran Airways and two other airlines are offering a holiday gift to travelers: Free Wi-Fi in the sky.

Starting Saturday , AirTran, Delta Air Lines and Virgin America will give away broadband Internet connections on domestic flights. The deal will last until Jan. 2.

This means passengers can use for their Wi-Fi-enabled devices — smart phones, tablets and laptops — as they soar 30,000 feet above the Earth.

Google Chrome is sponsoring the free Wi-Fi, which typically costs between $4.95 and $12.95, depending on the length of the flight and device. Travelers can't make phone calls but they can access the Web, do last minute online-shopping or check Facebook.

Last year, Google teamed up with Virgin America for the holiday promotion but expanded it this year to include other airlines equipped with Gogo Inflight Internet service.

Providing Wi-Fi access in the air works differently than on the ground. Gogo Inflight Internet uses wireless signals provided by Aircell Networks, which covers the entire country.

Instead of pointing the equipment on cell towers toward the ground, it aims skyward to connect with devices on planes. A plane's altitude and the amount of network traffic could affect signal strength, according to Gogo.

The use of Wi-Fi on airplanes has really taken off in the past two years, analysts say.

The number of planes built to handle Wi-Fi has grown from a few dozen in 2008 to 2,000 by the end of this year, according to In-Stat, a market-research firm that released a study this summer about the in-flight broadband market.

Promotions such as the one Google Chrome is sponsoring are good ways to introduce passengers to in-flight broadband, said Amy Cravens, an analyst who authored the In-Stat study. But the number of users significantly dropped once the promo ended, she said.

This year, about 2 percent of passengers paid for the service this year, she said, in part because Wi-Fi was only in a few planes.

"Now, though there is consistency in availability and the public is becoming more familiar with the offering so it will be interesting to see if usage climbs in 2011," Cravens said.

AirTran spokeswoman Cynthia Tinsley-Douglas said AirTran has done a couple of Wi-Fi promotions this year, but there are no plans to provide free Wi-Fi year round.

Sarah Lundy can be reached at 407-420-6218 or slundy@orlandosentinel.com. Follow her on Twitter at http://www.twitter.com/OSsarahlundy.